Pencil lead and poisoning

Dear Matthew Alice: How do they get the lead into a wood pencil? And how come we don’t get lead poisoning as children by doing all that schoolwork in pencil? — J.H., El Cajon

Where have you been for the last 400 years, J.H.? You've got some catching up to do. Actually, the lead-in-a-pencil question is a classic. It’s the one bit of “common knowledge” that practically everybody knows is wrong. And because we think we're clever enough not to be fooled by this “fact,” we’re convinced that everything else we know is right. Each of us somehow, somewhere has learned that there isn’t any lead in a lead pencil, so we smugly figure we’re immune to other bad facts. (We base this on the assumption that everybody else believes there is lead in a pencil. Wrong. Nobody else believes that. Well, almost nobody.) If we aren’t fooled by that one, we figure, then we must have some inside track on reality. But of course, that belief is just one more bad fact.

To bring you up to speed, J.H., here’s the dope on pencils. True enough, a lump of lead or lead shaped into a sort of stylus was once used as a marking device. But the lines it made were faint and its applications were limited. Pen and ink were the writing standards through the late 1500s. Aside from its erasability, the only advantage to lead was its portability, so mankind was ripe for some marking device that approached the blackness of ink without the problems of toting around an inkwell.

As the story goes, one day in the late 1500s an Englishman noticed some odd rocks unearthed by the roots of a fallen tree. When he picked them up, a black substance rubbed off on his fingers. He’d discovered what’s now called graphite, though it was first called “black lead.” (If records are accurate, the first thing ever marked with graphite was not paper but sheep. Apparently the farmer used the black stones to make a primitive sort of brand on his animals.)

Pure, high-quality English graphite made a clear black mark on virtually any surface, so it quickly replaced lead in what passed in those days for pencils. But because graphite was called black lead for at least another century, the erroneous name stuck and persists to this day. So we don’t get lead poisoning from pencil leads because they are actually a mixture of graphite powder, fine-grained clay, and a medium like oil or wax. Each manufacturer has its own formulas, depending on what the pencil is designed for. Pencil leads have been pure graphite or a graphite amalgam for four centuries.

As for how the lead gets inside the wood, here’s the technique as it was in 1600: The graphite amalgam was shaped into a skinny stick, a lengthwise channel was cut into a cedar slat, the graphite was glued into the channel, a second piece of cedar was glued on to enclose it, then the wood was smoothed and shaped to fit the hand comfortably. And in the last 400 years, how far has pencilmaking technology advanced? Well, today the pencil lead is glued into a channel cut in a piece of cedar, a second piece is glued on, and the wood is smoothed and shaped to fit the hand comfortably. It’s one of the few things we human beans seem to have gotten right almost immediately and left well enough alone ever since. The only flurry of excitement in the world of pencilmaking occurred in the late 1850s, when someone got the idea of sticking an eraser onto one end.